5.32 A ZEBRAFISH MODEL FOR IDENTIFYING COMMON BIOLOGICAL MECHANISMS AND PHARMACOLOGICAL PATHWAYS IN AUTISM SPECTRUM DISORDERS

Objectives: The goal of this research is to understand common biological mechanisms underlying ASD. By capitalizing on the advantages of zebrafish as a model organism, our objective is to progress from gene discovery to molecular mechanisms disrupted in ASD and finally to the identification of potential pharmacological targets. Methods: We generated zebrafish mutants in nine high confidence ASD risk genes using Zinc Finger Nucleases, TALENs, and CRISPR/Cas9 technology. We generated mutations in the zebrafish ortholog of CHD8, one of the strongest ASD risk genes identified to date, in order to elucidate the function of this gene in the developing nervous system. We analyzed excitatory and inhibitory neuronal populations as well as head and body size in chd8 mutants at a series of neurodevelopmental time points. Lastly, we conducted highthroughput 3-day rest-wake behavioral analysis of zebrafish larvae. Results: We found that chd8 homozygous mutants display a trend towards a 10-20 percent decrease in forebrain and hypothalamic neurons when compared to wild-type and heterozygous siblings. Homozygous mutants also display a significant decrease in body size at 2 months old. Finally, chd8 homozygous mutants display a specific behavioral fingerprint of a decrease in daytime rest bout length. Conclusions: These data provide evidence regarding the feasibility of using a zebrafish model to elucidate the function of genes disrupted in ASD and to identify neural circuits that are disrupted in neurodevelopmental disorders.